1. Field of the Invention
This invention relates to a process of producing an improved aluminun alloy product for use in making heat exchanger fins, and a fin stock material so-produced having a tailored corrosion potential and preferably high conductivity.
2. Background Art
Aluminun alloys have long been used in the production of heat exchanger fins, e.g. for automotive radiators, condensers, evaporators etc. Traditional radiator fin alloys are designed to give high strength after brazing, good brazeability and a good sag resistance during brazing. Alloys used for this purpose usually contain a high level of manganese. An example is the aluminum alloy AA3003. Such alloys provide a good brazing performance; however, the thernal conductivity is relatively low. Low thermal conductivity has not been a serious problem in the past because of the significant thickness of the finstock material. If the material is of suitable thickness it can conduct a significant quantity of heat. However, in order to make vehicles lighter in weights there is a demand for thinner finstock material, and this has emphasised the need for improved thermal conductivity. Obviously, thinner gauge materials tend to impede heat flux as they become thinner.
Heat exchangers as well are designed for good corrosion performance, and this is frequently accomplished by making the fins of a material with a lower corrosion potential (more negative) than the remainder of the heat exchanger (making the fins sacrificial) and the fin material must therefore be tailored to the appropriate corrosion potential.
In the past, changes in the corrosion potential and conductivity of alloys have been brought about by changing the chemical composition of the alloys. For example, the inventors of the present application have previously found that specific aluminum alloys are particularly suitable for use in finstock material (as discussed in Applicants' prior unpublished U.S. patent application Ser. No. 09/121,638 filed Jul. 23, 1998, which is assigned to the same assignee as the present application, and which is incorporated herein by reference). These alloys contain Fe, Si, Mn and usually Zn and optionally Ti in particular content ranges. However, an improvement in the corrosion potential of heat exchanger made using fins of alloys of test kid and also an improvement in the thermal conductivity would make these and related alloys even more useful in meeting the stringent demands of the automotive industry.